1. Field of the Invention
The present invention relates to a shift lock unit which is utilized to prevent misoperation of a shift lever or an automatic transmission o an automobile.
2. Description of the Related Art
In a conventional shift lever device of an automatic transmission of an automobile, as illustrated in FIG. 17, a shift lever 300 is pivoted in the direction of arrow A around a pivot shaft 302 provided at the bottom end of the shift lever 300. The position at which a grooved pin 304, which pivots together with the shift lever 300, engages with a detent groove 307 of a detent plate 306 is thereby changed, so that a P position, an R position, an N position, a D position and the like can successively be obtained. In order to shift from the P position, at which the shift lever 300 is vertical, to another position, it is necessary to push a shift lever knob button 308 and move the grooved pin 304 downward in the axial direction of the shift lever (i.e., in the direction of arrow B) so that the grooved pin 304 crosses over a convex portion 310 at the detent groove 307 of the detent plate 306.
Here, in order to prevent misoperation of the shift lever 300, a shift lock unit which prevents shifting from the P position to another position is provided. Due to this unit, if the shift lever knob button 308 is pushed when the brake is not depressed, the grooved pin 304 is not moved downward in the axial direction of the shift lever.
In a conventional shift lock unit, as illustrated in FIGS. 18 and 19, a metal bracket 316 is formed so as to be bent into a horizontal portion 312 and a vertical portion 314. A shift lock plate 318 is disposed so as to oppose the vertical portion 314 of the bracket 316. Two guide holes 320 are provided at the shift lock plate 318, one guide hole 320 being provided at the top of the shift lock plate 318 and the other being provided at the bottom thereof. The guide holes 320 are formed so as to be elongated in the vertical direction. Two guide pins 322, which are formed at the top and bottom of the vertical portion 314 so as to correspond to the guide holes 320, are fixed to the vertical portion 314 so as to protrude therefrom, and engage with the respective guide holes 320. As the grooved pin 304, which engages with an engagement concave portion 324 at the upper end portion of the shift lock plate 318, moves downward in the axial direction of the shift lever, the shift lock plate 318 is guided so as to move in the same direction.
A stopper 326 is disposed to oppose the horizontal portion 312. A stopper shaft 328 is provided at an intermediate portion of the stopper 326. By pivoting the stopper 326 around the stopper shaft 328, an engaged state and a separated state can be obtained. In the engaged state, a lock portion 327 at one end portion of the stopper 326 enters into the lower end surface of the shift lock plate 318 and engages with the shift lock plate 318. In the separated state, the lock portion 327 exits from the lower end surface of the shift lock plate 318 and separates from the shift lock plate 318. In the engaged state, downward movement of the shift lock plate 318 is not possible, movement of the grooved pin 304 downward in the axial direction of the shift lever is prevented, and shifting from the P position to another position is not possible. In the separated state, downward movement of the shift lock plate 318 is possible, and movement of the grooved pin 304 downward in the axial direction of the shift lever is permitted. After the grooved pin 304 is moved downward in the axial direction of the shift lever, by pivoting the shift lever 300, the grooved pin 304 separates from the engagement concave portion 324 of the shift lock plate 318, crosses over the convex portion 310 of the detent groove 307 of the detent plate 306, and movement to another position is possible.
A solenoid 330 (stopper driving means) is mounted to the horizontal portion 312. A fitting hole 334 is formed at the tip end portion of a plunger 332 (moved/driven shaft) of the solenoid 330. An operation pin 336 which protrudes from the other end portion of the stopper 326 fits in the fitting hole 334. When the solenoid 330 is operated, the plunger 332 is pulled in, and the stopper 326 pivots from the engaged state of being engaged with the shift lock plate 318 to the separated state.
A shift lock control switch 338 (detecting switch) is mounted to the vertical portion 314. The shift lock control switch 338 accommodates a contact holder 342 within a switch cover 340, and is closed by a circuit plate 344 having fixed contacts (unillustrated) at the inner surface thereof. The contact holder 342 is provided with an engagement pin 348 which engages with an engagement hole 346 of the shift lock plate 318. The contact holder 342 can move together with the shift lock plate 318, and is provided with moving contacts 350 which contact the fixed contacts of the circuit plate 344. Due to the contact holder 342 moving together with the shift lock plate 318, the moving contacts 350 change the fixed contacts of the circuit plate 344 which contact the moving contacts 350. The shift lock plate 318 can thereby output a P position detection signal which detects the P position in which the shift lock plate 318 is at the upper position.
An unillustrated shift lock control computer is further provided. The shift lock control computer is connected to the solenoid 330 and the shift lock control switch 338 via separate connectors 352, 353 respectively, and is connected to a stop lamp switch. When the shift lever 300 is at the P position and the brake is depressed so that the stop lamp switch is on, the solenoid 330 is operated. When the brake is not depressed and the stop lamp switch is off, even if the shift lever 300 is at the P position, the solenoid 330 is not activated, and shifting from the P position to another position is prevented when the brake is not depressed.
Further, a shift lock release lever 354 (shift lock release portion) is provided at the shift lock unit. The intermediate portion of the shift lock release lever 354 fits with the leading end portion of the upper guide pin 322 so that the shift lock release lever 354 pivots freely around the guide pin 322. The bottom end portion of the shift lock release lever 354 engages with an operation piece 356 which is provided upright from one end portion of the stopper 326. Even if the solenoid 330 is not operated, the stopper 326 can be forcibly pivoted so that the stopper 326 separates from the shift lock plate 318, by pushing an operation portion 358 at the upper end of the shift lock release lever 354 against the urging force of a torsion coil spring 360 and pivoting the shift lock release lever 354.
In the above-described conventional shift lock unit, the solenoid 330 and the shift lock control switch 338 are connected to the shift lock control computer via the separate connectors 352, 353 provided respectively thereat. The number of structural parts therefore increases correspondingly, which leads to an increase in size.
Further, two guide pins 322 which move and guide the shift lock plate 318 in the vertical direction are provided. Therefore, a corresponding wide space is necessary, which also results in an increase in size. In addition, the movement of the shift lock plate 318 in the vertical direction is guided by the two guide pins 322 of the bracket 316 and by the two guide holes 320 of the shift lock plate 318. The position of the shift lock plate 318 in the moving direction of the stopper 326 is regulated by the mounting of the shift lock plate 318 to the bracket 316. Therefore, the amount of movement of the plunger 332 of the solenoid 330 necessary to reach the separated state from the engaged state at which the stopper 326 and the shift lock plate 318 are engaged, is influenced and differs in accordance with the dimensional accuracy of the bracket 316, the shift lock plate 318, the stopper 326, the solenoid 330 and the like forming the shift lock unit, and in accordance with the assembly accuracy of these components, and the like. In such cases, in order to ensure the engagement and separation of the stopper 326 and the shift lock plate 318, the amount of movement of the plunger 332 of the solenoid 330 must be set in advance so as to be large and so as to have a certain margin. This leads to a further increase in size.
The bracket 316 is metal and is press-worked. This results in an increase in size caused by the management of the materials and the like.
Because the stopper 326 pivots, the region of movement thereof is large, which also results in an increase in size.
The shift lock release lever 354 is provided separately from the stopper 326 and pivots, resulting in an increase in size. Because there are many parts, costs also increase.
Further, between the fitting hole 334 of the leading end portion of the plunger 332 and the operation pin 336 at the other end portion of the stopper 326, there is separation of the contact between the fitting hole 334 and the operation pin 336 when the solenoid 330 is operated. This results in generation of striking sounds.